This section is intended to provide a background or context to the disclosed embodiments. The description herein may include concepts that could be pursued, but are not necessarily ones that have been previously conceived or pursued. Therefore, unless otherwise indicated herein, what is described in this section is not prior art to the description and claims in this application and is not admitted to be prior art by inclusion in this section.
Wireless communication systems are widely deployed to provide various types of communication content such as voice, data, and so on. These systems may be multiple-access systems capable of supporting communication with multiple users by sharing the available system resources (e.g., bandwidth and transmit power). Examples of such multiple-access systems include code division multiple access (CDMA) systems, time division multiple access (TDMA) systems, frequency division multiple access (FDMA) systems, 3GPP Long Term Evolution (LTE) systems, and orthogonal frequency division multiple access (OFDMA) systems.
Generally, a wireless multiple-access communication system can simultaneously support communication for multiple wireless terminals. Each terminal, or user equipment (UE), communicates with one or more base stations through transmissions on the forward and reverse links. The forward link (or downlink) refers to the communication link from the base stations to the user equipment, and the reverse link (or uplink) refers to the communication link from the user equipment to the base stations. This communication link can be established through a single-in-single-out, multiple-in-single-out or a multiple-in-multiple-out (MIMO) system.
It is customary to use timing control mechanisms in such multiple-access communication systems to provide synchronization of the uplink and downlink transmissions to fall within certain tolerances. For example, such a synchronization is needed to avoid interference between the user equipment with uplink data that are scheduled to be transmitted during the same information unit (e.g., a subframe of the communication system).
In some systems, the base station (or eNodeB) provides timing control information to allow a user equipment to adjust the timing of its uplink transmissions. However, such timing control information may not always be available to the user equipment. In addition, the synchronization between the uplink and downlink transmissions may become skewed or lost due to system and tracking tolerance errors and/or when a new timing control information is issued while the user equipment is still in the process of effecting a previous timing control command. As a result, the transmission of a particular uplink information unit may overlap with the transmission of an adjacent information unit. In another scenario, a gap may be created between the transmission of a particular uplink information unit and the transmission of an adjacent information unit. The presence of such gaps and overlaps can lead to a reduction in system throughput and inefficient use of network resources due to, for example, loss of transmitted data, additional retransmission requests and additional computational resources to detect and correct transmission errors and to maintain synchronization.